My habits of documenting correspondence with anyone outside my office, particularly when money or reputation are involved, pre-date fusion. For that matter it predates email, when everything was done on paper. But I digress.
I'm unlikely to send a full working model to a client or fabricator. There's not much in there they really need (unless they are paying me for the actual parametric model, but that's not the norm for me). THAT version gets saved in an appropriate location and documented as the file that was sent and received. And THAT version never gets changed again. it becomes a reference document.
Of course I make version notes in my working model as to what was sent, etc. But that's useless to someone outside of my office. particularly if they don't use fusion, or don't have a great understanding of how the "cloud" works. And heaven forbid things get in to the legal realm (been lucky so far). "look, see, that's the version we all agreed on, see it says right there in my comments. wait, what? I have to freeze my entire account to insure I don't change anything during legal discovery?!"
If it makes sense to carry on from where I am in MY model, I certainly will. or I my save it out to create a branch design direction. Or I may start over. multiple times. Now I have a directory full of files with similar names, all with various version comments. Quite a web of info. Not something I want to explain to customers or clients. When the client or fabricator starts saying things like "I thought we were going to do this or that " and has obviously started to confuse the facts of the project, it's important to be able to trace back to a specific file that was sent out. having multiple files with similar names, each with multiple versions and comments, doesn't really serve that purpose well.